1-{(E)-[4-(4-Methoxyphenyl)butan-2-ylidene]amino}-3-methylthiourea

Two independent molecules comprise the asymmetric unit of the title compound, C13H19N3OS, which differ in the conformations of the residues linking the thiourea and the terminal benzene ring, as manifested in the Cm—Cm—Ca—Ca torsion angles [78.03 (16) and −93.64 (16)°, respectively; m = methylene and a = aromatic]. The dihedral angles [84.40 (4) and 88.28 (5)°] formed between the thiourea residue and the benzene ring indicate an almost orthogonal relationship. In each thiourea residue, the N—H hydrogen atoms are anti, and the terminal N—H hydrogen atom forms an intramolecular N—H⋯N hydrogen bond with the imine-N atom. In each case, the conformation about the imine C=N double bond [1.2812 (17) and 1.2801 (17) Å] is E. In the crystal, the molecules are connected by N—H⋯S hydrogen bonds and these are connected into four molecule aggregates via N—H⋯O hydrogen bonds, which are assembled into a two-dimensional array parallel to (011) via C—H⋯π and π–π interactions [ring centroid–centroid distance = 3.8344 (9) Å].

Two independent molecules comprise the asymmetric unit of the title compound, C 13 H 19 N 3 OS, which differ in the conformations of the residues linking the thiourea and the terminal benzene ring, as manifested in the C m -C m -C a -C a torsion angles [78.03 (16) and À93.64 (16) , respectively; m = methylene and a = aromatic]. The dihedral angles [84.40 (4) and 88.28 (5) ] formed between the thiourea residue and the benzene ring indicate an almost orthogonal relationship. In each thiourea residue, the N-H hydrogen atoms are anti, and the terminal N-H hydrogen atom forms an intramolecular N-HÁ Á ÁN hydrogen bond with the imine-N atom. In each case, the conformation about the imine C N double bond [1.2812 (17) and 1.2801 (17) Å ] is E. In the crystal, the molecules are connected by N-HÁ Á ÁS hydrogen bonds and these are connected into four molecule aggregates via N-HÁ Á ÁO hydrogen bonds, which are assembled into a twodimensional array parallel to (011) via C-HÁ Á Á andinteractions [ring centroid-centroid distance = 3.8344 (9) Å ].   Table 1 Hydrogen-bond geometry (Å , ).

Crouse and Edward R. T. Tiekink Comment
To initiate comparative studies between hydrazinecarbothioamide Schiff bases (Zhang et al., 2011) and hydrazinecarbodithioate derivatives synthesized in our laboratory in on-going investigations (Khoo et al. 2005;Chan et al. 2008;Ravoof et al., 2010), the title compound was synthesized and characterized crystallographically.
In each case, the methoxy group is co-planar with the benzene ring to which it is connected as seen in the values of the C13-O1-C10-C9 and C26-O2-C23-C22 torsion angles of 175.41 (12) and -5.62 (19)°, respectively. In each thiourea residue, the N-H hydrogen atoms are anti, and the terminal N-H hydrogen atom forms an intramolecular N-H···N hydrogen bond with the imine-N atom, Table 1. The conformation about the imine C═N double bond [N3═C3 = 1.2812 (17) Å and N6═C16 = 1.2801 (17) Å] is E in each case.

Experimental
The title compound was synthesized following established literature procedures (Tian et al. 1997;Tarafder et al. 2002).
To 4-methyl-3-thiosemicarbazide (1.05 g, 10 mmol) dissolved in hot absolute ethanol (25 ml) was added an equimolar amount of 4-(4-methoxyphenyl)butan-2-one (1.70 ml) also in hot absolute ethanol (20 ml). The mixture was stirred for about half an hour at ~340 K and then cooled to room temperature. The Schiff base precipitated was filtered and dried in vacuo over anhydrous silica gel. Colourless crystals were obtained after one week from a 1:1 mixture of 2-propanol and absolute ethanol. Yield 76%, M.pt. 356 K.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H = 0.95 to 0.99 Å) and were included in the refinement in the riding model approximation with U iso (H) set to 1.2 to 1.5U equiv (C). The amino H-atoms were refined with a distance supplementary materials sup-2 . E68, o1461-o1462 restraint of N-H = 0.88±0.01 Å, and with U iso (H) = 1.2U eq (N).

Figure 1
The molecular structure of the two independent molecules in (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level. Hydrogen bonds are shown as dashed lines.

Figure 2
An overlay diagram of two independent molecules in (I). The S1-containing molecule is illustrated in red and the S2molecule in blue. Molecules have been aligned so that the N1,S1,N2 and N4,S2,N5 planes are overlapped.   A view in projection down the a axis of the unit-cell contents for (I). The N-H···S, N-H···O, C-H···π and π-π interactions shown as blue, orange, brown and purple dashed lines, respectively. Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.